Shock wave treatment method and apparatus



Feb.

1959 N. e. BRANSON 3,429,743

v SHOCK WAVE TREATMENT METHOD AND APPARATUS Filed Nov. 1'7. 1966 F l G.1 5 Z ./|2 :=:"T FIG. 2

NORMAN 5. BRANSON INVENTOR.

United States Patent 3,429,743 SHOCK WAVE TREATMENT METHOD AND APPARATUSNorman G. Branson, Stamford, Conn., assignor to Branson Instruments,Incorporated, Stamford, Conn., a corporation of Delaware Filed Nov. 17,1966, Ser. No. 595,112

US. Cl. 134-1 18 Claims Int. Cl. B08b 3/10 ABSTRACT OF THE DISCLOSUREMethod and apparatus providing high intensity shock waves caused byelectrical spark discharges in a sonically degassed liquid for thepurpose of cleaning, sterilization, etc. The sonic energy means causingdegassing and the electrical discharge circuit means may be operatedsimultaneously or sequentially.

This invention refers to a method and apparatus for subjecting a liquid,or articles confined therein, to high intensity shock waves. Moreparticularly, the present invention concerns a method and apparatuswhich employs high energy shock waves propagated in a liquid andproduced by electrical discharges for treating articles. Such treatmentmay comprise sterilization, disloding of particles, removal of surfacesoil and the like.

While the prior art shows various arrangements for producing highintensity shock waves resulting from electrical discharges, the methodand apparatus used heretofore have not been particularly effectivebecause gas absorbed in the liquid has impeded the forceful propagationof such shock waves. The method and apparatus described hereinafterattempt to overcome this heretofore existing shortcoming by includingmeans for degassing the liquid, hence, providing an improved arrangementwhich accomplishes more work in relation to the input power. Moreover,the arrangement disclosed hereafter is suited particularly for cleaningof parts. For instance, it is well known that ultrasonic cleaning ismost effective for removing soil and contamination from the surface ofarticles. However, when heavy contamination, such as rust orcarbonaceous deposits, is involved, the ultrasonic energy propagated inthe cleaning liquid is not possessed of sufiicient power to remove suchdeposits.

As has been found these deposits can readily be dislodged by theapplication of repetitive high intensity shock waves which result fromelectrical discharges in the cleaning liquid. Therefore, both processescan advantageously be used to cause first the removal of heavy andstrongly adhering contaminants using high intensity shock waves,followed by the more gentle sonic or ultrasonic cleaning method forremoving the remaining smaller and finer contamination still adhering tothe article surface. Hence, heavily contamination articles may becleaned to a fine degree in a single step method.

One of the principal objects of this invention is, therefore, theprovision of an improved arrangement for treating articles using highintensity shock waves.

Another important object of this invention is the provision of animproved method and apparatus for cleaning articles by high intensityshock waves using a substantially degassed cleaning liquid.

Another object of this invention is the provision of a cleaning methodwhich combines the desirable characteristics of high intensity shockwaves with those produced by ultrasonic cleaning.

A further important object of this invention is the provision of animproved method and apparatus for treating articles in a container whichis provided with electrical spark gap means and ultrasonic energy means.

Further and still other objects of this invention will be more clearlyapparent by reference to the following description when taken inconjunction with the accompanying drawings in which:

FIGURE 1 is an elevational view, partly in cross sectlon, of a typicalembodiment of the invention;

FIGURE 2 is a sectional view of the typical spark gap device used inconnection with FIGURE 1;

FIGURE 3 is a schematic diagram of the electrical circuit which providesthe electrical discharges for producing high intensity shock waves inthe liquid, and

FIGURE 4 is a sectional view of an alternative arrangement for treatinga liquid.

Referring now to the figures and FIGURE 1 in particular, numeral 12refers to a heavy-walled open-ended, tubular metal container 12 whichcontains a liquid 14. An article 16 to be treated, such as a heavilycorroded metal part, is suspended in the liquid 14 by a wire 18. Theliquid may be a caustic solution or another suitable cleaning liquid,preferably having a small amount of electrical conductivity. In atypical embodiment the container 12 is fitted with a set ofelectro-acoustic transducers 20 which are adapted to be energized by ahigh frequency generator 22 providing electrical current at 20 kHz. Thetransducers may be of the piezoelectric or of the magnetostrictive type.It should be understood that the frequency at which the transducers areoperating is not critical and frequencies in the lower or higher regionmay be used.

Additionally, the container 12 is fitted with a spark gap device 24which comprises, as seen in FIGURE 2, an insulating bushing 25 and acentral metal electrode 26. This spark gap device 24 is connected to anelectrical circuit 28 which, when energized, produces periodic pulses ofenergy. When a potential of sufiicient magnitude is applied between theelectrode 26 and the tank 12, an electrical discharge occurs betweenthis electrode and the tank wall, which discharge produces highintensity shock waves in the liquid 14. These shock waves impinge uponthe surface of the article 16, thereby causing gross contamination to bedislodged therefrom. In order to enhance the intensity of the shockwaves, avoiding the absorption of energy by entrained gas, the liquid 14is subjected to sonic or ultrasonic energy generated by the transducers20, such energy, as is known, causing a degassification of the liquid.This degassification process may be carried out either prior to theoperation of the spark gap discharge device or concurrently therewith,depending upon the circumstances. Alternatively, both energy devices maybe operated in alternate manner.

A typical electrical circuit for connection to the spark gap device 24is shown in FIGURE 3. It should be clearly understood that the circuitmay serve to energize several spark gap devices connected in paralleland provided on the container 12, although for the sake of simplicityonly one such device is illustrated. The circuit comprises a chargingcircuit which includes a transformer 30, a bridge rectifier 32, a seriesinductance 34 and a capacitor 36. The discharge circuit comprises twoseries connected controlled rectifiers 38 connected to the capacitor 36and two indutcances 40 and 42. The capacitor 36 periodically is chargedwith direct current from the rectifier 32 and is discharged through theseries connected rectifiers and the spark gap device. In this way thereis produced a train of electrical discharges, each discharge causing thepropagation of a high intensity shock wave in the liquid 14, and, as isknown, such shock wave, in turn, by reflection generates additionalshock waves.

The embodiment per FIGURE 1 is well suited for cleaning parts which areheavily corroded. The sonic energy produced by the transducers 20 notonly degasses the liquid to enhance the effect of the high intensityshock waves but causes also a fine scrubbing of the surface of article16. Hence, heavy contamination which requires high impact forces may beremoved by the high intensity shock waves, While follow-up cleaning isdone with the sonic energy, preferably operating at a power level whichproduces cavitation in the liquid 14.

The entire process may advantageously be carried out in a singlecontainer. The procedure comprises (a) immersing the article 16 in theliquid 14; (b) degassing the liquid 14 by operating the transducers 20;(c) repetitively producing high intensity shock waves =by firing thespark gap device 24 until coarse particles are dislodged from thearticle surface, and (d) finishing the cleaning of the article surfaceunder the influence of sonic or ultrasonic energy propagated from thetransducers 20. In this last step, it is desirable that there existscavitation in the liquid. Obviously steps (c) and ((1) may be combinedto be effective substantially simultaneously.

FIGURE 4 shows an alternative arrangement which is particularly adaptedfor treating a flowing liquid or particles suspended within the liquid.Numeral 50 refers to a section of a pipe through which the liquid 14flows. A spark gap device 24 is mounted into the pipe wall andtransducers 20A and 20B are mounted at either side. In order to ventliberated gas, a vent valve 52 is provided. Liquid can be treated as itflows past this treatment station.

While there have been described and illustrated certain preferredembodiments of my invention, it will be apparent to those skilled in theart that various changes and modifications may be made without departingfrom the broad principle and scope of my invention.

What is claimed is:

1. The method for treating an article in a liquid comprising the stepsof:

(a) immersing the article surface to be treated in the liquid, and whilesaid surface is immersed,

(b) subjecting said liquid to:

(b-l) sonic energy of suflicient intensity to cause degassification, and

(b-2) high intensity shock waves resulting from electrical spark gapdischarges produced within said liquid.

2. The method for treating an article as set forth in claim 1 whereinsaid sonic energy and said shock waves are produced sequentially.

3. The method for treating an article as set forth in claim 1 whereinsaid sonic energy and said shock Waves are produced substantiallyconcurrently.

4. The method for treating an article as set forth in claim 1 whereinsaid sonic energy is of an intensity sufficient to cause cavitation insaid liquid.

5. The method for treating an article as set forth in claim 1 whereinsaid sonic energy is in the ultrasonic frequency range.

6. The method for treating an article as set forth in claim 1 whereinsaid liquid is a cleaning solution.

7. The method for treating an article as set forth in' claim 1 whereinsaid liquid is stationary.

8. The method for treating an article as set forth in claim 1 whereinsaid liquid is flowing while being subjected to said sonic energy and tosaid high enregy shock waves.

9. The method for treating an article as set forth in claim 1 whereinsaid liquid is electrically conductive.

10. The combination of:

a container adapted to hold a liquid;

sonic energy means coupled to said container for imparting sonic energyto the liquid disposed in said container, and

electrical spark gap discharge means coupled to said container forcausing in said liquid high intensity shock waves.

11. The combination per claim.10 wherein said sonic energy meanscomprises electro-mechanical transducers and an electrical highfrequency generator coupled thereto for supplying electrical energy tosaid transducers.

12. The combination per claim 11 wherein said sonic energy means isadapted to cause cavitation in said liquid.

13. The combination per claim 10 wherein said spark gap discharge meanscomprises a spark gap device in contact with the liquid and anelectrical circuit for causing periodic firing thereof.

14. The combination per claim 13 wherein said sonic energy meanscomprises a set of electro-mechanical transducers straddling said sparkgap device.

15. The combination per claim 10 wherein said container holds astationary quantity of liquid.

16. The combination per claim 10 wherein said container is a section ofa pipe and the liquid is adapted to flow therethrough while said sonicenergy means and said discharge means are actuated.

17. The combination per claim 16 wherein said pipe section is fittedwith a gas vent valve for discharging gas liberated by the operation ofsaid sonic energy means.

18. The combination per claim 10 wherein said container is metal andsaid discharge means produces an electrical discharge between anelectrode in contact with the liquid and the container.

References Cited UNITED STATES PATENTS 2/1966 Olson 1341 XR 11/1966Ploeger et al. 55277 XR US. Cl. X.R.

